Theory of doubly resonant infrared-visible sum-frequency and difference-frequency generation from adsorbed molecules

Abstract

We theoretically analyze doubly resonant infrared-visible sum-frequency (DR IVSFG) and diferencefrequency generation (DR IVDFG) from a monolayer of adsorbates at an interface. Our calculated results with a model molecule indicate that the resonant amplitude of nonlinear optical susceptibility of DR IVDFG and DR IVSFG processes conveys information about the electron-vibration coupling in adsorbates. Moreover, owing to a dephasing-rephasing procedure involved, DR IVDFG can also be developed into a sensitive probe for investigating the coherent phase relaxation process in adsorbed molecules without the complication of inhomogeneous broadening.PACS number(s): 42.50.Md, 68.35.Ja

Identification of chemical species of fluorescein isothiocyanate isomer–I (FITC) monolayers on platinum by doubly resonant sum‐frequency generation spectroscopy

“…SFG in such a condition is called DR-SFG. 7,8 DR-SFG spectroscopy has been applied to a number of systems such as a spin-coated dye film on silica, 8 C 60 monolayer on silver, 9 and a colored protein monolayer on platinum 10 with visible probes, and a benzene derivative on gold with UV probes. 11 DR-SFG also allows detection of chirality of thin films.…”

In situ nonlinear optical spectroscopy of electron–phonon couplings at alkali‐doped C60/Ag(111) interfaces

“…In a two-colour SFG experiment, the visible laser frequency is tuneable as well. In this case, the SFG signal can be further enhanced by an electronic resonance if the output SFG frequency v SFG matches an electronic transition [13][14][15][16]. The enhancement depends critically on the electron-phonon coupling between the vibrational mode and the electronic levels involved in the electronic transition [13,16].…”

“…The latter contains both singly resonant and doubly resonant contributions to the SFG signal. A double SFG resonance occurs when the SFG signal is enhanced simultaneously by coupled vibrational and electronic transitions [13][14][15][16]. In this case, singly resonant contributions are negligible and DR-SFG takes place for several visible frequencies when v IR ¼ v Q and when v SFG matches simultaneously an allowed vibronic transition to the excited electronic level (Fig.…”

Energy Conservation and the Manley-Rowe Relations in Surface Nonlinear-Optical Spectroscopy

“…An enormous progress has been achieved in experimental applications of the surface nonlinear-optical spectroscopy to study different systems [4]. On the other hand, although a number of theoretical studies of surface SHG [5][6][7][8] and a few extensions of the theory to surface SFG spectroscopy [9][10][11] have been reported, there are still various unsolved problems in understanding the fundamental physics of the surface nonlinear interactions. For threewave interactions in centrosymmetric bulk media the energy relations were first considered by Pershan [12], who constructed the free energy for transparent centrosymmetric systems with quadrupole-allowed nonlinearity.…”